The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Catalytic converters are used in an exhaust system of an internal combustion engine (ICE) to reduce emissions. As an example, a three-way catalyst converter (TWC) reduces nitrogen oxide, carbon monoxide and hydrocarbons within an exhaust system. The three-way converter converts nitrogen oxide to nitrogen and oxygen, carbon monoxide to carbon dioxide and oxidizes unburnt hydrocarbons to produce carbon dioxide and water.
An average light off temperature at which a catalytic converter typically begins to function is approximately 200-350° C. As a result, a catalytic converter does not function or provides minimal emission reduction during a warm up period that occurs upon a cold start up of an engine. Operating temperatures of a catalytic converter may be approximately 650-900° C. after the warm up period. Efficiency of a catalytic converter improves with an increase in operating temperature. For the stated reasons, the quicker a catalytic converter increases to the light off temperature upon a cold start the better the emission reduction performance of an exhaust system.
Hybrid electric vehicles may include an ICE and one or more electric motors. The ICE may have an exhaust system with a catalytic converter. The ICE may be deactivated repeatedly and/or for extended periods of time to conserve fuel. Temperature of the catalytic converter decreases when the ICE is deactivated. A start/stop vehicle includes and deactivates an ICE during, for example ICE idle periods and/or when velocity of the start/stop vehicle is 0 m/s. As a result, a catalytic converter may provide limited emission reduction performance upon starting of a hybrid electric vehicle and a start/stop vehicle.